Microwave heaters or dielectric heaters are devices used for heating loads incorporating a microwave absorbent matter. Generally, the microwave heater has a magnetron (or microwave generator) for generating waves into a cavity wherein the load is to be positioned. As the waves exhibit multiple reflections inside the cavity, standing waves are established therein. These standing waves, when oscillating at a high frequency, create rotation in the molecular dipoles and cause vibration of the molecules and thus generate heat.
Standing waves in a multimode cavity are characterized by having portions where the electric field is null (i.e., nodes or cool spots) and portions where the electric field is maximum (i.e. anti-nodes or hot spots). Therefore, when the load spatially extends from a node to an anti-node, non-uniform heating may occur. This can be problematic as one may want to heat either a large load or multiple loads uniformly all at once. The ‘spot’ issue is typically addressed by providing the microwave heater with a turntable which rotates the substance to be heated during operation. However, turntables add mechanical complexity to microwave heaters and increase costs.
There is therefore a need for improved microwave heating systems and methods.